This is most likely a hardware fault, not a settings issue. On compact cameras like the Canon IXUS, exposure problems that change with zoom position often point to a damaged flex/ribbon cable in the lens assembly.

That cable helps control parts of the lens system as it extends and zooms. If it is failing, the camera may not correctly control the aperture or report lens position, which can cause severe overexposure at the telephoto end while appearing normal at wide angle.

Because the problem remains after a factory reset and occurs in multiple exposure modes, moisture or metering settings are less likely than a physical lens-related issue.

The practical fix is professional repair of the lens assembly/flex cable. If repair cost is high relative to the camera’s value, replacement may make more sense.